Origin of an enigmatic regional Mio-Pliocene unconformity on the Demerara plateau

The Demerara plateau, located offshore French Guiana and Suriname, is part of a passive transform continental margin particularly prone to develop slope instabilities, probably in relation to the presence of a free distal border along its steep continental slope. Slope failure occurred at different periods (Cretaceous to Neogene) and shows an overall retrogressive evolution through time. Upslope these failure headscarp, an enigmatic regional MioPliocene unconformity has been discovered through the interpretation of new academic and industrial datasets. The aim of this work is to describe and understand the origin of this surface. Our analysis shows that this unconformity is made of a series of valleys that cross-cut sedimentary strata. Each one of these valleys has a short lateral extent and is closed along two perpendicular directions, which suggests that it could correspond to a highly meandering system, or to some sub-circular depressions. The infill of these features is equivalent to the regional stratigraphic strata found outside the structures, but in a subdued position. This seems to imply that the structures have originated by a local loss of sediments at their base or by sliding processes. Furthermore, these depressions intersect each other through time, while migrating progressively downslope. We discuss a series of hypotheses that try to explain the onset and evolution of these depressions forming the Mio-Pliocene unconformity (Canyons? Slope failures? Contourite moats? Hydrate pockmarks?). Having established that these structures are depressions formed by collapse, and have many similarities with structures recently described in the literature as pockmarks associated with gas hydrate dissolution, we favor this hypothesis. We propose that these hydrate pockmarks form with a mass failure that was triggered by fluid-overpressure development at the base of the hydrate stability zone.

Ecoviability for small-scale fisheries in the context of food security constraints

This paper applies a stochastic viability approach to a tropical small-scale fishery, offering a theoretical and empirical example of ecosystem-based fishery management approach that accounts for food security. The model integrates multi-species, multi-fleet and uncertainty as well as profitability, food production, and demographic growth. It is calibrated over the period 2006–2010 using monthly catch and effort data from the French Guiana's coastal fishery, involving thirteen species and four fleets. Using projections at the horizon 2040, different management strategies and scenarios are compared from a viability viewpoint, thus accounting for biodiversity preservation, fleet profitability and food security. The analysis shows that under certain conditions, viable options can be identified which allow fishing intensity and production to be increased to respond to food security requirements but with minimum impacts on the marine resources.

Entre limites e distanciamentos : alguns aspectos das formações de coletivos “Waiwai” e percursos etnológicos pela Amazônia Oriental

Dissertação (mestrado)—Universidade de Brasília, Instituto de Ciências Sociais, Departamento de Antropologia, Programa de Pós-Graduação em Antropologia Social, 2015.

Le polar de la Caraïbe francophone : enjeux de l’appropriation du genre

Pour minoré et ignoré qu’il fût, le roman policier est désormais légitimé par l’institution littéraire. À parcourir les livres publiés dans la Caraïbe francophone, le genre demeure dans la marge de cette production [issue de la Caraïbe francophone (Haïti, Guadeloupe, Guyane française, Martinique)]. Quoiqu’il en soit, on notera que les années 1990 ont inauguré une véritable éclosion de publications de polars. Tout cela augure d’une acclimatation de ce genre qui ne s’accompagne pas moins de questionnements sur les spécificités éventuelles du polar caribéen francophone. Se situe-t-il dans la convention? Tente-il au contraire d’établir une distanciation avec la norme? C’est pour répondre à ces interrogations que cette thèse se propose d’explorer les enjeux de l’appropriation du polar provenant de cette aire géographique. À l’aune de la poétique des genres, de la sociocritique et de l’intermédialité, un corpus composé de quatorze romans fait l’objet d’une étude approfondie. Dans le premier chapitre, un bref récapitulatif permet de situer les œuvres à l’étude dans l’histoire littéraire du genre tout en soulignant l’adaptation du polar dans la Caraïbe de langue française. Il en ressort qu’un nombre significatif d’écrivains, attentifs à la latence du magico-religieux dans leur société, mettent en scène le surnaturel alors que le roman policier conventionnel plébiscite la méthode logico-déductive. C’est la raison pour laquelle le second chapitre s’intéresse à l’usage de l’inexplicable et son rapport avec le cartésianisme. Quant au troisième chapitre, il se penche sur un topos du genre : la violence telle qu’elle surgit dans ses dimensions commémoratives et répétitives de l’histoire tumultueuse de la Caraïbe. Notre corpus tend à relier la notion du crime, fut-il d’emprise originelle, à l’histoire post-coloniale. Dans la mesure où les personnages constituent un élément clé du genre, ils sont sondés, dans un quatrième chapitre, en regard de la critique sociale qu’ils incarnent et véhiculent. Le dernier chapitre cherche à circonscrire l’intermédialité qui structure et qualifie l’œuvre au sein du roman policier depuis sa genèse. Somme toute, ces divers axes contribuent à mieux comprendre le phénomène de transposition du polar dans cette région du monde.

A methodological framework to assess the carbon balance of tropical managed forests.

Background: Managed forests are a major component of tropical landscapes. Production forests as designated by national forest services cover up to 400 million ha, i.e. half of the forested area in the humid tropics. Forest management thus plays a major role in the global carbon budget, but with a lack of unified method to estimate carbon fluxes from tropical managed forests. In this study we propose a new time- and spatially-explicit methodology to estimate the above-ground carbon budget of selective logging at regional scale. Results: The yearly balance of a logging unit, i.e. the elementary management unit of a forest estate, is modelled by aggregating three sub-models encompassing (i) emissions from extracted wood, (ii) emissions from logging damage and deforested areas and (iii) carbon storage from post-logging recovery. Models are parametrised and uncertainties are propagated through a MCMC algorithm. As a case study, we used 38 years of National Forest Inventories in French Guiana, northeastern Amazonia, to estimate the above-ground carbon balance (i.e. the net carbon exchange with the atmosphere) of selectively logged forests. Over this period, the net carbon balance of selective logging in the French Guianan Permanent Forest Estate is estimated to be comprised between 0.12 and 1.33 Tg C, with a median value of 0.64 Tg C. Uncertainties over the model could be diminished by improving the accuracy of both logging damage and large woody necromass decay submodels. Conclusions: We propose an innovating carbon accounting framework relying upon basic logging statistics. This flexible tool allows carbon budget of tropical managed forests to be estimated in a wide range of tropical regions

INDÚSTRIA SUCRO-ALCOOLEIRA NA ARGENTINA, NO BRASIL E O CONTEXTO DOS BIO-COMBUSTÍVEIS NO CONTINENTE AMERICANO

O objetivo desse artigo é abordar aspectos relacionados à produção e ao consumo de biocombustíveis – sobretudo bio-etanol - no continente americano, analisando as seguintes áreas: Estados Unidos; América Central, Caribe e América do Sul – com maior ênfase para Brasil e Argentina. Para nos atentarmos ao tamanho limite de páginas, deixaremos de abordar algumas experiências interessantes, como as de Peru, Colômbia, México, Guatemala e Guiana, entre outras. 

NOS CAMINHOS DA RAPOSA SERRA DO SOL (RORAIMA): A REGIÃO, FORMAS DE CONTEMPLAÇÃO, USOS E APROPRIAÇÕES

O objetivo deste trabalho é desenvolver uma análise regional contribuindo às formas de contemplação, usos e apropriações da paisagem do Território Indígena da Raposa Serra do Sol, por meio de desdobramentos fundamentados nos contextos sociais, culturais, econômicos e geográficos de uma área caracterizada por inconsistências e incertezas. O estudo, focado no nordeste do Estado de Roraima, abrange os municípios de Normandia, Uiramutã e Pacaraima, na região da tríplice fronteira Brasil - República Cooperativa da Guiana (ex Guiana Inglesa) - República Bolivariana da Venezuela. A área territorial é de 1.747.465 ha. Nessa perspectiva, tomou-se aqui a leitura da categoria geográfica ‘região’ e o trabalho empírico, buscando entender as limitações e necessidades de definição fundiárias das terras do Estado roraimense. Estas dificultam o delineamento de ações sob a ótica da preservação/conservação da natureza e cultura do norte brasileiro. Enfim, tais apontamentos não são específicos da região a ser considerada neste estudo, assim como também não o são suas implicações carregadas de contradições, uma vez que essas relações e entrelaçamentos são vistos e abordados em outras partes do mundo globalizado